I still have a copy of Apple stores 2009 Quad prices, the upgrade from 2.66 to 3.33 GHz Quad was around $1,400 in Japan. So assuming you have the low end Quad it is just a little more than that to upgrade, around $1,500. It may not be a great deal right now, but if they still offer this a year and half from now, some people may jump on it.
With the dollars devaluation as compared with Yen it would cost me the same as people who live in the states to upgrade my low end 2009 Quad. But, I only thought about it for a few seconds, a little too expensive for me, besides I like new with all the bells and whistles that go with that. (USB 3, Sandy Bridge, a year and half from now, who knows what we will have, the middle of 2012, Beam me down.)